Rendered mode all black
A few issues with your file:

You have a big cube.001 that is not visible in the viewport (eye icon) but that is rendereable (camera icon) that blocks everyting. Get rid of it.

Then you have an object (cube) that is a big block of glass and volume scatter. The volume scatter is set at a value of 0.2. bring it down to 0.05 and you'll see your objects will start to show.

What are you trying to accomplish with the glass shader? Unplug it.

If you are looking for the reflection of the water surface use a different plane for that.

Then you have a bunch of objects called circle.xxx that are disabled for render and that have materials done in blender internal. You have to recreate those materials in order to use them in cycles.

The edges of the big cube that you are using as water is visible in the shot. Is this a pond or a fish tank?

Why is the lamp inside the water? Also, the light was set using blender internal materials and in cycles it needs to be an emission shader. And it needs to be quite bright to compensate for the volume scatter in the water.